iio: invensense: fix multiple odr switch when FIFO is off

iio: invensense: fix multiple odr switch when FIFO is off

When multiple ODR switch happens during FIFO off, the change could
not be taken into account if you get back to previous FIFO on value.
For example, if you run sensor buffer at 50Hz, stop, change to
200Hz, then back to 50Hz and restart buffer, data will be timestamped
at 200Hz. This due to testing against mult and not new_mult.

To prevent this, let's just run apply_odr automatically when FIFO is
off. It will also simplify driver code.

Update inv_mpu6050 and inv_icm42600 to delete now useless apply_odr.

Fixes: 95444b9eeb8c ("iio: invensense: fix odr switching to same value")
Cc: stable@vger.kernel.org
Signed-off-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
Link: https://patch.msgid.link/20241021-invn-inv-sensors-timestamp-fix-switch-fifo-off-v2-1-39ffd43edcc4@tdk.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>